Meeting Abstract
27.1 Saturday, Jan. 4 13:30 Variation in tensile properties of tracheal tubes in the American cockroach BECKER, W. R.*; WEBSTER, M. R.; SOCHA, J. J.; DE VITA, R.; Virginia Tech; Virginia Tech; Virginia Tech; Virginia Tech wbecker@vt.edu
Insects use an extensive network of tracheal tubes to transport oxygen directly to cells throughout the body. These tubes are made of an outer layer of epithelial cells and an inner layer of spirally- or circumferentially-wound folds called taenidia. The taenidia, which are composed of chitin fibers embedded in a protein-rich matrix, provide structural integrity to the tracheae. Despite this structural support, localized compression of tracheae is known to occur during respiratory ventilation in multiple species of insects. Interestingly, only some portions of tracheal tubes appear to deform during a compression event. These localized deformations, which displace volume and therefore contribute to the transport of gasses within the body, may result from variation in the structural and mechanical properties of the tracheae. To better understand the role of tracheal properties on respiratory compression, we conducted mechanical tests on ring sections of tracheal tubes extracted from American cockroaches (Periplaneta americana). We successfully tested a total of 33 specimens from 14 thoracic tracheal tubes using a custom-built tensile testing system. The ultimate tensile strength (22.6±13.3 MPa), ultimate strain (1.57±0.68 %), elastic modulus (1740±840 MPa), and toughness (0.175±0.156 MJ/m3) were measured. The large variation in mechanical properties was examined statistically using bootstrap methods, demonstrating that ring sections excised from the same tracheal tube exhibit comparable mechanical properties. Our results will form the basis for future studies aimed at determining the structure-function relationship of insect tracheae, ultimately improving our understanding of respiratory transport mechanisms in insects. Supported by NSF 0938047.
